Systems and methods for vacuum-forming aspheric mirrors

ABSTRACT

A method of forming a 3D mirror for a heads-up display (HUD) system includes providing a glass-based preform having a first major surface, a second major surface, and a minor surface connecting the first and second major surfaces, and further includes disposing the glass-based preform on a mold having a concave surface such that the first and second longitudinal side surfaces are adjacent to a longitudinal wall of a housing. The longitudinal wall extends from the concave surface to at least a height of the second major surface of the glass-based preform. The method further includes supplying a vacuum and conforming the second major surface to the concave surface of the mold using the vacuum. The first and second transverse side surfaces have a curved shape corresponding to a curve of the concave surface a remain coincident with the concave surface during the conforming of the second major surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of PCT Application No.: PCT/KR2018/015092filed on Nov. 30, 2018, which claims the benefit of priority under 35U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/592,570 filedon Nov. 30, 2017, the content of which is relied upon and incorporatedherein by reference in its entirety

TECHNICAL FIELD Background Art

Head-Up Display or Heads-Up Display (HUD) systems project visualinformation onto a transparent surface so that users can see theinformation without diverting their gaze away from their primary view.HUD systems typically use a mirror to reflect and project an image ontothe transparent surface. One application for HUD systems is intransportation, such as automobiles, aircraft, marine craft, and othervehicles. For example, HUD systems can be deployed in vehicles so thatan operator or driver of the vehicle can see information relevant to theoperation of the vehicle while maintaining a forward gaze and withouthaving to look down or away towards a display screen. Thus, HUD systemsare believed to improve safety by minimizing the need for a vehicleoperator to look away from a safe operating viewpoint.

However, HUD systems have often suffered from poor optical quality inthe projected image, which may result in an undesirable aestheticquality to the projected image. Poor optical quality may even decreasethe safety of HUD systems, because blurry or unclear projected imagescan make it more difficult for users to read or understand the projectedinformation, resulting in increased user processing time of theinformation, delayed user reaction time based on the information, andincreased user distraction. Reduced optical quality can result from asub-optimal mirror used in the HUD system, often resulting from impropershaping of the mirror or defects introduced into the mirror duringcurving of a mirror preform.

Thus, there remains a need for HUD systems, and particularly improvedmirrors for HUD system, that have improved optical quality, as well asimproved methods of forming such mirrors.

DISCLOSURE OF INVENTION Technical Problem

There remains a need for HUD systems, and particularly improved mirrorsfor HUD system, that have improved optical quality, as well as improvedmethods of forming such mirrors.

Solution to Problem

In some embodiments of the present disclosure, a method of forming athree-dimensional mirror for a heads-up display (HUD) system isprovided. The method includes providing a glass-based preform having afirst major surface, a second major surface opposite to the first majorsurface, and a minor surface connecting the first and second majorsurfaces, the minor surface including first and second longitudinal sidesurfaces opposite to each other and first and second transverse sidesurfaces connecting the longitudinal side surfaces. The method includesdisposing the glass-based preform on a mold having a concave surfacesuch that the second major surface faces the concave surface of themold, and such that the first and second longitudinal side surfaces areadjacent to a longitudinal wall of a housing, the longitudinal wallextending from the concave surface to at least a height of the secondmajor surface of the glass-based preform. The method also includessupplying a vacuum to a gap between the second major surface and theconcave surface, and conforming the second major surface to the concavesurface of the mold using the vacuum. The first and second transverseside surfaces have a curved shape corresponding to a curve of theconcave surface such that the first and second transverse side surfacesremain coincident with the concave surface during the conforming of thesecond major surface.

In additional embodiments of the present disclosure, an apparatus forforming a three-dimensional mirror for a heads-up display (HUD) isprovided. The apparatus includes a mold comprising a concave surfacewith at least one opening configured to supply a vacuum to a space abovethe concave surface when a glass-based preform is disposed on the mold,and a housing adjacent to and at least partially surrounding the concavesurface. The housing extends from the concave surface to at least aheight of the glass-based preform when the mirror preform is disposed onthe mold, and the housing is sized to prevent leakage of the vacuum at aportion of the space between the glass-based preform and the concavesurface.

In other embodiments of the present disclosure, a method of forming anaspheric mirror from a two-dimensional glass-based preform is provided.The method includes providing a glass-based preform comprising a firstmajor surface, a second major surface opposite the first major surface,and a minor surface connecting the first and second major surfaces. Theminor surface includes first and second longitudinal side surfacesopposite to each other and first and second transverse side surfacesconnecting the longitudinal side surfaces the glass-based preform havinga substantially two-dimensional shape. The method also includesdisposing the glass-based preform on a lower mold comprising a curvedsurface having an aspheric shape facing the second major surface, thelower mold being configured to supply a vacuum to a gap between thecurved surface and the second major surface, and performing a primaryforming step by supplying vacuum pressure to the gap while a shellsurrounds the glass-based preform such that a substantially verticalwall of the shell extends from the curved surface to at least the secondmajor surface, the substantially vertical wall facing the minor surface.The substantially vertical wall of the shell is spaced from the minorsurface at a distance to improve the vacuum pressure in the gap. Themethod can further include a secondary forming step by applying aclamping-ring to a periphery portion of the first major surface to holdthe second major surface against the curved surface at the peripheryportion, where the second forming step is performed while the lower moldis supplying a vacuum to the gap.

Additional features and advantages of the claimed subject matter will beset forth in the detailed description which follows, and in part will bereadily apparent to those skilled in the art from that description orrecognized by practicing the claimed subject matter as described herein,including the detailed description which follows, the claims, as well asthe appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the presentdisclosure, and are intended to provide an overview or framework forunderstanding the nature and character of the claimed subject matter.The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated into andconstitute a part of this specification. The drawings illustrate variousembodiments and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

For the purposes of illustration, there are forms shown in the drawingsthat are presently preferred, it being understood, however, that theembodiments disclosed and discussed herein are not limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is an illustration of HUD system in a vehicle according to someembodiments of the present disclosure.

FIG. 2 is an illustration of an automobile driver's viewpoint when usingthe HUD system of FIG. 1 , according to some embodiments.

FIG. 3 is a photograph of a combiner used in some HUD systems accordingto some embodiments of the present disclosure.

FIG. 4 is an illustration of an automobile driver's viewpoint when usinga HUD system with a combiner similar to the one shown in FIG. 3 ,according to some embodiments.

FIG. 5 is a plan view of a 2D mirror preform and a resulting asphericmirror formed from the 2D mirror preform according to some embodiments.

FIG. 6 is an isometric view of a 2D mirror preform on a bending moldaccording to some embodiments.

FIG. 7 is a schematic representation of a 2D reference planecorresponding to a 2D preform before undergoing a 3D forming step and a3D mirror after undergoing the forming step.

FIG. 8 is an isometric illustration of an aspheric mirror for a HUDsystem according to some embodiments.

FIG. 9 is an isometric view of a 2D mirror preform on a forming mold,according to some embodiments.

FIG. 10 is a cross-section schematic of a gap between a forming mold andan edge of a preform during forming.

FIGS. 11A and 11B are isometric views of examples of housing assembliesused for improved forming of a curved mirror.

FIG. 12 is a plan view of a rectangular mirror preform (top) and a planview of a mirror preform with curved end edges (bottom) according tosome embodiments.

FIG. 13A shows an isometric view of the rectangular mirror preform ofFIG. 12 on a forming mold.

FIG. 13B shows an isometric view of the mirror preform with curved endedges of FIG. 12 on a forming mold, according to some embodiments.

FIGS. 14A and 14B show cross-section views of the long-side andshort-side edges, respectively, of the rectangular mirror preform ofFIG. 13A on a forming mold.

FIGS. 15A and 15B show cross-section views of the long-side andshort-side edges, respectively, of the mirror preform with curved endedges of FIG. 13B on a forming mold, according to some embodiments.

FIGS. 16A and 16B show isometric and plan views, respectively, of ahousing used with a mirror preform having a curved end edge according tosome embodiments.

FIG. 17 is an isometric view of another housing used with a mirrorpreform having a curved end edge according to some embodiments.

FIG. 18 is a cross-section view of a system and method for forming acurved mirror using a mirror preform and housing according to someembodiments.

FIGS. 19A and 19B are isometric and cross-section views of aclamping-ring for forming a curved mirror according to some embodiments.

FIG. 20 is a cross-section view of a system and method for forming acurved mirror using a mirror preform and clamping-ring according to someembodiments.

FIG. 21 is a photograph of an example curved mirror formed according toembodiments of the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.

Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range. As used herein, the indefinite articles “a,”and “an,” and the corresponding definite article “the” mean “at leastone” or “one or more,” unless otherwise specified.

The following description of the present disclosure is provided as anenabling teaching thereof and its best, currently-known embodiment.Those skilled in the art will recognize that many changes can be made tothe embodiment described herein while still obtaining the beneficialresults of the present disclosure. It will also be apparent that some ofthe desired benefits of the present disclosure can be obtained byselecting some of the features of the present disclosure withoututilizing other features. Accordingly, those who work in the art willrecognize that many modifications and adaptations of the presentdisclosure are possible and may even be desirable in certaincircumstances and are part of the present disclosure. Thus, thefollowing description is provided as illustrative of the principles ofthe present disclosure and not in limitation thereof.

Those skilled in the art will appreciate that many modifications to theexemplary embodiments described herein are possible without departingfrom the spirit and scope of the present disclosure. Thus, thedescription is not intended and should not be construed to be limited tothe examples given but should be granted the full breadth of protectionafforded by the appended claims and equivalents thereto. In addition, itis possible to use some of the features of the present disclosurewithout the corresponding use of other features. Accordingly, thefollowing description of exemplary or illustrative embodiments isprovided for the purpose of illustrating the principles of the presentdisclosure and not in limitation thereof and may include modificationthereto and permutations thereof.

HUD systems can be used to provide a wide variety of types ofinformation for improved safety and convenience of users. Intransportation, for example, information relevant to vehicle operation,such as vehicle gauges or navigation, can be projected to an area infront of a driver. This can include real-time information on vehiclespeed, fuel level, climate control settings, entertainment settings,turn-by-turn navigation indicators, estimated time of arrival, andalerts related to speed, traffic, or dangerous conditions. Informationcan be presented as text, symbols, pictures, videos, animation, and oneor more colors. These are examples only, and embodiments of thisdisclosure are not intended to be limited to these examples.

In some embodiments of the present disclosure, a HUD system can includean image generating device and one or more optical components fordirecting or projecting an image from the image generating device to anarea that is easily visible to a user. The image generating device caninclude a cathode ray tube (CRT) display, a light-emitting diode (LED)display, a liquid crystal display (LCD) assembly, laser projectionsystem, or other type of display known by those of ordinary skill in theart. The HUD system may also include a computer or processor forgenerating the images produced by these displays. The optical componentsmay include some combination of lenses, beam splitters, mirrors, andcombiner, for example. The combination of components of a HUD system canbe configured to produce collimated light.

The collimated light is projected onto a combiner that is in a field ofview of a user so that the user can see the projected image and thenormal field of view simultaneously. For example, in vehicularapplications, the combiner can be a windshield. Alternatively, thecombiner can be a separate component that is built into the vehicle, ora portable component that can be mounted in the vehicle in a locationwhere a driver or passenger can see the projected image on a transparentsurface of the combiner. The mirror can include a reflective coating ona curved substrate. The curved substrate may be spherical, aspherical, aFresnel shape, and/or diffractive. In one preferred embodiment, themirror has a reflective surface or coating on a concave, asphericalsurface.

FIG. 1 shows an example of a HUD system 100 according to someembodiments of the present disclosure. The HUD system 100 is shown in anautomobile, but embodiments can be used in various vehicles ornon-vehicular applications. A driver D is shown with hands on thesteering wheel W of the vehicle V. The HUD system 100 is incorporatedinto the dash 110 of the vehicle V, and includes a programmablegraphical unit (PGU) 102 connected to an image source 103 configured toproduce an image based on a signal from the PGU 102. The PGU 102 mayinclude a processor operably connected to a non-transient,computer-readable storage medium containing instructions that, whenexecuted, generate and/or supply data for generating a image by theimage source 103 to be displayed by the HUD system 100. That image isreflected by a flat mirror 104 towards a curved mirror 106. From thecurved mirror 106, the image is projected toward the windshield 108 andonto a projection area 112 of the windshield 108. The HUD system 100 canbe configured so that the projection area 112 is within the normal lineof sight of the driver D while driving the vehicle V. For example, theprojection area 112 can be positioned so that the projected image isoverlaid on the road as seen from the driver's perspective. An exampleof this scenario is shown in the illustration of FIG. 2 .

While the projection area 112 is located on the windshield 108 in FIGS.1 and 2 , FIGS. 3 and 4 show an alternative embodiment in which acombiner 208 is used for the location of the projection area 212. Thecombiner 208 can be built into the dash 210 of a vehicle or can be aportable or separable component that is positioned on top of the dash210.

Embodiments of this disclosure are not limited to one or more particulararrangements of the optical components of a HUD system, as persons ofordinary skill in the art will understand the basic arrangement ofcomponents in a HUD system. The present disclosure is directed primarilyto the curved mirrors used in HUD systems, and to systems and methodsfor forming such mirrors. In particular, embodiments are directed tosystem and methods of forming such three-dimensional (3D) mirrors fromtwo-dimensional (2D) mirror preforms. FIG. 5 shows an example of a 2Dmirror preform 300 that can be used to form a 3D mirror 302 usingsystems and methods discussed herein.

There are various systems and methods conventionally used for forming 3Dmirrors. However, the authors of the present disclosure realized thatimprovements were needed in the design of and the methods of forming thecurved mirrors used in HUD systems. To prevent degradation of imagequality as the image is reflected by the curved mirror, the mirrorshould have a high level of shape accuracy and surface roughness. Forexample, a shape precision of less than 50 μm and a surface roughness(Ra) of less than 3 nm is desirable. A particular type of opticaldistortion that occurs in mirrors for HUD systems is referred to as edgedistortion, which is optical distortion of light reflected at or nearthe edge of the mirror. In existing HUD systems, optically impactfulimperfections may be introduced into the mirror during manufacturing orshaping of the mirror. These imperfections can include artifacts such asraised or lowered portions created by equipment in the manufacturing ofthe mirrors, or imperfections in the curvature of the mirror,particularly in the curvature at or near the edges of the mirror.

The most common methods for forming 3D-shaped mirrors or mirrorsubstrates can be divided into two categories: pressing methods andvacuum-forming methods. Both pressing and vacuum-forming methods,however, can have disadvantages. In a pressing method, upper and lowermolds are used to press the substrate, such as a glass substrate, byphysical force. For example, the upper mold may be pressed into a lowermold with a 2D glass preform disposed between the two molds, and theglass preform is formed according to the shape of a surface on one orboth of the molds. As a result, mold imprints may be left on both theconcave and convex surfaces of the formed glass substrate, which thenrequires polishing. In addition, due to deviations in the contours ofthe upper and lower molds, it can be difficult to precisely match thecontours of the upper and lower molds, and thus difficult to achieve aprecise shape for the formed glass substrate. For example, thespecification for aspheric mirror contours can be less than ±25 μm,while the mold contour deviation after machining is normally 30-50 μm.

In a vacuum forming method, a single mold (e.g., lower mold) can beused, where vacuum holes are formed in the surface of the mold. Forexample, as shown in FIG. 6 , a flat (2D) glass sheet or 2D preform 300is disposed on or above the forming surface 312 of the mold 310 andvacuum pressure is supplied via the vacuum holes 314 to conform themirror preform to the curved (3D) surface of the mold. The formingsurface 312 is shaped to a desired shape of the 3D mirror. However, itis difficult to avoid the formation of vacuum hole marks on the surfaceof the formed glass substrate. These vacuum hole marks or manufacturingartifacts can impair the optical performance of the substrate or thefinished mirror. In addition, typical vacuum forming methods can requirehigher forming temperatures compared to pressing methods. Higher formingtemperatures can affect surface quality and form defects such asdimples, pits, and imprints. Vacuum forming can be performed on a mirrorpreform, which is a substrate that is pre-cut to the desired size beforeforming into a 3D shape with vacuum forming, or on an oversized sheet ofglass, which is cut to the desired size after forming into a 3D shapewith vacuum forming. Both preform-based and oversized-glass-based vacuumforming have certain advantages and disadvantages.

Oversized-glass-based forming, for example, has advantages of achievinggood edge quality due to edge cutting, and good surface roughness due tolower forming temperatures. However, oversized-glass-based formingrequires the added steps of cutting the glass after forming; has lowglass utilization due to trim glass or waste glass after forming;requires edge polishing and/or chamfering after cutting; and requireslarger equipment even though the eventual finished product may be thesame size as that formed in preform-based forming.

On the other hand, in preform-based vacuum forming, there is no need tocut the mirror substrate after vacuum forming, which reduces theproduction of waste or cullet glass. In addition, preform-based formingcan be a more simple process and more cost effective. However, in apreform-based vacuum forming method, it has been difficult or impossibleto apply a relatively uniform vacuum pressure over the entire surface ofthe glass sheet due to vacuum leaks at one or more edges of the glasspreform, due at least in part to vacuum leakage between the preform andthe mold. For example, if the formed glass is to have a single radius ofcurvature, the short-side edge of the preform may maintain contact withthe mold surface until forming is complete, but the vacuum will leakalong the long-side edge of the preform. In the case of more complexcurvature or an aspheric mold surface (and aspheric formed substrate),only discrete points of the glass sheet, such as the four corners, maycontact the mold surface throughout forming, which results in vacuumleakage along all edges of the glass substrate. Also, for forming anaspheric mirror, it is possible for the corner of the mirror or mirrorsubstrate to chip or break, which occurs when only the corners of themirror substrate are in contact with the mold and an external force(e.g., vacuum pressure, mold pressing force) is applied, thusconcentrating pressure at the four corners of the substrate. In somecases, such as when the forming surface is not aspheric but has a singleradius of curvature, the short-side edge of a preform may maintainbetter contact with the forming surface until forming is completed, buta vacuum leak can occur along the long-side edge of the preform. Thesegaps or leaks in vacuum pressure make it difficult or impossible toprovide relatively uniform vacuum pressure to the entire surface of themirror or preform. As such, higher forming temperature (and lowerviscosity of the substrate) is used to conform the glass onto the moldsurface more completely, and to reduce the stress near the corners toreduce chipping. However, as discussed above, higher temperatures causesurface degradation of the glass substrate and decreased opticalperformance. Even with higher temperatures, edge distortion of themirror occurs.

Investigators behind the present disclosure have discovered systems andmethods to improve the mirrors formed using vacuum-based formingmethods. In some preferred embodiments, these techniques may beparticularly well-suited for the preform-based forming methods. However,some embodiments are not limited to mirrors made using the preform-basedforming methods, nor even to vacuum-based methods, generally. Oneproblem addressed by the embodiments of the present disclosure is thatof edge distortion. As mentioned above, when using vacuum formingmethods, it can be difficult to achieve a uniform vacuum and uniformconformation of the mirror substrate to the mold. It can be particularlydifficult to conform the mirror substrate to the desired shape at ornear the edges of the substrate, which causes edge distortion anddegrades the quality of the image reflected by the mirror near the edge.Therefore, embodiments of the present disclosure provide mirrors and/ormirror substrates with improved optical performance, including at theedge, and methods of forming the same.

The mirrors in HUD systems generally have an aspheric reflectivesurface, which can include a reflective coating formed on an asphericsurface of a mirror substrate. As discussed above and shown in FIG. 7 ,a 3D mirror 400 may be formed from a 2D mirror preform 420. As arectangular preform, the mirror preform 420 has a long-side edge 402 anda short-side edge 404. In forming the 3D mirror, the long-side edge 402and the short-side edge 404 bend to conform to the forming mold. Basedon the shape of the forming mold, as determined by the desired shape ofthe resulting 3D mirror, the linear distance between opposite short-sideedges 404 decreases, and the magnitude of the decrease between theshort-side edges may differ from that of the long-side edges. Anaspheric or aspherically shaped surface has multiple radii of curvature.In particular, in the case of a four-sided mirror as shown in FIGS. 7and 8 , for example, an aspheric surface has a different radius ofcurvature along each of the four edges. Thus, as shown in FIG. 8 , amirror 400 has a reflective surface 408 that is aspherically shaped witha radius of curvature Ra along a first edge, a radius of curvature Rbalong a second edge, a radius of curvature Rc along a third edge, and aradius of curvature Rd along a fourth edge. Because the surface 408 isaspherically shaped, Ra≠Rb≠Rc≠Rd. In addition, Rb and Rd may be lessthan Ra and Rc. Due to the differences in curvature of the long-sideedges as compared to the short-side edges, a change in the distancebetween the short-side edges 404 due to forming may be greater than anydecrease of the distance between opposite long-side edges 402 due to thesmaller radii of curvature Rb, Rd on the long-side edges and the largerradii of curvature Ra, Rc on the short-side edges. This can make it moredifficult to prevent leaking of the vacuum pressure along the short-sideedge. FIG. 8 also shows how different points on the curved surface 408have been displaced by varying amounts a-e with respect to atwo-dimensional plane 406 connecting the four corners of the mirror 400.In some embodiments, a≠b≠c≠d. In one example, displacements a-e may beequal to the following: a=7.73, b=6.32, c=6.52, d=1.31, and e=1.31,where the displacements are given in unitless, relative magnitudes, butthe units of displacements a-e may be in millimeters. Thetwo-dimensional plane 406 comprises a minor axis 408 between oppositelong-side edges of the 2D preform and a major axis 410 between oppositeshort-side edges of the 2D preform.

As shown in FIG. 9 , when a 2D mirror preform 420 is disposed on aforming mold 430, only the corners of the mirror preform 420 may contactthe forming mold 430 prior to a conforming the preform 420 to formingsurface 432. As such, a gap remains between the mirror preform 420 andthe forming surface 432. In particular, a gap 434 remains between ashort-side edge 422 of the mirror preform 420 and a gap 436 remainsbetween a long-side edge 424 of the mirror preform 420. To the extentgaps 434 and 436 remain open during a conforming step of the preform 420to the forming surface 432, some of the vacuum suction from the vacuumholes in the forming surface 432 is lost. This can lead to sub-optimalconforming of the mirror preform 420 to the forming surface 432, andthus to a failure to achieve the desired shape of the 3D mirror.

FIG. 10 shows a cross-section view of an edge of a 3D mirror 420′ duringor after a step of conforming the 2D mirror preform 420 of FIG. 9 to theforming mold 430. While there may be good conformity between the formingsurface 432 and an interior portion of the 3D mirror 420′ near one ormore interior vacuum holes 438, a gap 434′ can remain near an edge ofthe 3D mirror 420′. As shown in FIG. 10 , gap 434′ can remain even whena vacuum hole 439 is located near the edge, because vacuum suction islost as a result of the gap 434′. As a result, the desired curvature ofthe 3D mirror 420′ is not achieved near the edge. Due to theabove-discussed challenges in maintaining precise control over the shapeof a 3D mirror formed by vacuum forming, the investigators of thepresent disclosure developed systems and methods capable of achievingimproved 3D mirrors. In particular, these systems and methods allow forimproved suction and forming at or near the edge of a 3D mirror usingvacuum forming of a 2D preform.

In some embodiments, as shown in FIG. 11A, a housing 500 can be usedduring a step of conforming a 2D preform to a 3D forming surface. Thehousing 500 forms a ring-like shape with side walls or sealing surfacesconfigured to be positioned at or near one or more edges of a mirrorpreform during the step of conforming to the vacuum mold. In FIG. 11A,the mold 500 includes short-side walls 502 and long-side walls 504,which in combination form a ring-like shape with a space in the middlethat is sized and shaped to contain a preform.

An example of a housing 540 positioned on a forming mold 530 is shown inFIG. 11B. The housing 540 surrounds the perimeter of the forming surfaceof mold 530 and defines a space in which the mirror preform 520 isplaced for forming. The housing 540 includes opposite short-side walls544, 545, and opposite long-side walls 542, 543. The housing 540operates to minimize vacuum leaking at the edges of the mirror preform520. The housing 540 does not necessarily need to touch the mirrorpreform 520 to improve vacuum performance. Indeed, it may beadvantageous in some embodiments for there to not be physical contactbetween the housing 540 and the preform 520 so that the preform 520 canmove without friction forces from the housing 540 that could negativelyimpact the finished product. The clearance between the inside walls ofthe housing 540 may be, for example, 0.5 mm or less, in someembodiments. However, this clearance can be adjusted based on thecoefficient of thermal expansion of the glass-based preform 520 and thehousing 540.

Even when using a housing as shown in FIG. 11B, it is possible that,during forming of the 2D preform into a 3D mirror, a gap can appear atone or more edges of the preform, which can result in loss of suctionnear the edge. For example, depending on the curvature of the formingsurface, there can be significant transverse movement of edges duringforming, as discussed above and shown in FIG. 7 . Thus, as theshort-side edges 404 of the preform 400 in FIG. 7 move toward eachother, the short-side edges 404 would correspondingly move away from ahousing provided around the preform 400, which can result in a gap atthe short-side edge 404. Accordingly, some embodiments include a preformhaving at least one edges shaped to coincide with a curvature of theforming surface where that edge of the preform meets the formingsurface. One example of such a preform is shown in the lower half ofFIG. 12 , where a standard, rectangular preform 600 is shown in the tophalf of FIG. 12 . Specifically, the preform 610 has an extended surfacearea 620 with a curved edge 614. The extended surface area 620 extendsbeyond a line L where the edge of the preform is located in a standardpreform 600, and the curved edge is shaped to coincide with a formingsurface. The curved edge 614 on the short-side edge allows the preform610 to keep sufficiently close contact between the preform 610 and theconcave surface of mold during forming. In other words, the short-sideedge, when curved, can maintain contact with the concave forming surfacefrom the start to the finish of the forming process. The curvature ofthe curved edge 614 can be composed of a single radius of curvature or aspline curve to more accurately follow the curvature of the top surfaceof the mold.

As used herein, “coincide” or “coincident” means that the curvature ofthe curved edge of the preform is an approximate match for a curvaturein the forming surface that is located at an intersection of the preformand the forming surface. The curve in the forming surface that iscoincident with the curved edge can be considered an intersection curvebetween the curved forming surface and a reference plane which containsthe 2D preform when placed on the mold. This is shown in FIG. 13B, wherepreform 610 is placed above the forming surface 613 of the mold 612.Whereas preform 600 in FIG. 13A has a straight short-side edge 604,preform 610 has a curved short-side edge 614 that is coincident with thecurvature of the molding surface 613 where the 2D preform 610 is placed.In one preferred example, the curvature of the short-side edge ofpreform 610 has approximately the same radius of curvature as theintersection curve. Because the extended surface area 620 is extendedfrom what is to become the effective area of the 3D mirror, theprojected image of the HUD mirror is not negatively affected by theextended area 620.

FIGS. 14A and 14B show cross-section views of the long-side edge andshort-side edge, respectively, of a standard preform 600 on a mold 602,where preform 600 has a straight or non-curved short-side edge 604. Forthe long-side edge, the direction of sagging (shown by the arrow in FIG.14A) during forming is substantially vertical, so that the long-sideedge does not move significantly away from the housing 608. As such,there is low risk of the vacuum hole 606 being exposed or losing vacuumpressure. On the other hand, the direction of sagging (shown by thearrow in FIG. 14B) can have vertical and horizontal components. Thehorizontal movement or shrinkage pulls the short-side edge away from thehousing 608 and threatens to reduce vacuum pressure near the short-sideedge. The distance x represents the relative short distance between theshort-side edge 604 and the vacuum hole 606. In contrast, FIGS. 15A and15B show cross-section views of the long-side edge and the short-sideedge, respectively, of a preform 610 according to embodiments of thisdisclosure. The preform 610 includes a curved short-side edge 614. Themovement of the long-side edge in FIG. 15A is substantially the same asdescribed for FIG. 14A. However, in FIG. 15B, there is a larger distancex′ between the housing 618 and the vacuum hole 616. This long distance,coupled with the curved edge that coincides with the forming surface ofthe mold 612, helds to ensure that vacuum pressure is maintained nearthe edge.

FIGS. 16A and 16B are perspective and plan views, respectively, showingthe preform 610 of FIGS. 15A and 15B with the curved short-side edge 614being used with a modified housing 630, according to some embodiments.The modified housing 630 has long-side walls 634 and short-side walls632, but the short-side walls 632 has curved inner surfaces to coincidewith the curved short-side edge 614 of the preform 610. However, in someembodiments, the short-side walls 632 of the housing 630 may not beneeded when used with preform 610, due to the improved vacuum suctionand reduction in suction loss at the curved short-side edge 614resulting from the curved edge. Thus, FIG. 17 shows another embodimentin which a housing 640 is provided with only long-side walls 644, and nowall coinciding with the curved short-side edge 614.

FIG. 18 shows an example method of vacuum forming a 3D mirror from a 2Dmirror preform using a housing for improved vacuum suction and reducedvacuum leakage. In FIG. 18 , an assembly line includes zones fordifferent steps of forming the 3D mirror. A 2D preform 750 is providedon a mold 752 having a curved forming surface (not shown). The mold 752is moved along rollers or other suitable means of conveyance throughvarious zones or steps in the forming process. In a heating zone ZH, oneor more heaters 756 are provided to heat the preform 750. As discussedabove, due to improvements in the embodiments of this disclosure, it ispossible to perform the molding of the 2D preform at lower temperaturesthan conventional vacuum forming techniques. Although the temperature inthe heating zone ZH is not particularly, limited, it can be low enoughso that the preform 750 does not reach a glass transition temperature Tgof the preform 750. In some embodiments, the temperature can be lessthan or equal to Tg−10° C. In other embodiments, the temperature can beless than or equal to Tg−20° C., or from Tg−20° C. to Tg−10° C. Theheaters 756 can be located above the preform 750 and mold 752 so thatthey are out of the way of the other forming equipment and can directheat to the surface of the preform.

Next, a first forming zone ZF1 is provided in which a housing 758 ispositioned to surround some or all of the edges of the preform 750 andvacuum pressure is supplied to the mold 752 to conform the preform tothe forming surface of the mold 752, which turns the 2D preform 750 intoa curved substrate 750′. This can be a primary forming step, which canbe followed by additional forming steps, as discussed below. Asdiscussed above, the housing 758 is provided for improved vacuumpressure, particularly around the edges of the preform 750 or curvedsubstrate 750′. Methods can include provided the housing 758 by loweringit from a raised position P1 to a lower position P2. When lowered to P2,the housing 758 can be lowered onto a support surface 760 configured tohold and support the housing. During this step of vacuum forming, heatcan continue to be supplied by heaters 756, but at a relatively lowtemperature due to the improved and even vacuum supplied with the helpof the housing 758. Although not shown in FIG. 18 , the preform 750 canbe a preform having curved short-side edges for increase vacuum moldingperformance. In the second forming zone ZF2, vacuum pressure and/orheating can still be applied to the primary formed substrate 750″ foradditional and/or optional further steps.

In some embodiments, additional steps in the above method include theuse of a force applied at or near the of a mirror preform or primarilyformed mirror for improved edge forming and shape. FIGS. 19A and 19Bshow a clamping ring 765 as one example embodiment for applying the edgeform. As shown in FIG. 19A, the clamping ring 765 has short-side walls766 and long-side walls 767 forming a ring-like shape with a space inthe middle. The walls 766 and 767 have curved bottom surface that aredesigned to correspond to the curvatures along the edges of the desired3D mirror or to the curvature of the forming surface of mold 752directly below walls 766 and 767. Thus, as shown in FIG. 19B, the curvedshort-side edge 766 can apply a downward force on the edge of preform750 during forming to achieve improved edge shape by conforming the edgeto the forming surface and preventing vacuum leaks at the edge fromvacuum holes 753. Although FIG. 19A shows a clamping ring 765 with fourwalls having curved bottom surfaces, it is contemplated that a clampingring may be applied to only some or a portion of the edges of a preform.

FIG. 20 shows an alternative view of the method and assembly line shownin FIG. 18 . In particular, the second forming zone ZF2 includes aclamping ring 765. The clamping ring 765 is lowered by a clamping-ringsupport member 768 from a position P1 above the preform 750′ to aposition P2 on the preform 750′. After the second forming zone ZF2, thepreform 750″ can move to a cooling zone ZC or cooling step.

Although FIGS. 18 and 20 illustrate methods on a linear assembly line,the steps or zones ZH, ZF1, ZF2, and ZC may or may not be performing indifferent physical locations. For example, the clamping ring and housingmay be used without moving the preform from one location to another.Furthermore, the housing and clamping ring can be used simultaneouslyduring forming. In addition, the illustration of the clamping ring 765in FIGS. 19A and 19B is an example only. The mechanism for providing theforce to conform the edges of a preform to a forming surface can takemany forms.

FIG. 21 is a photograph of an example of a 3D mirror 800 formed usingdevices and methods discussed above, included a preform with a curvedshort-side edge.

Example

Using the above-described methods, as shown in FIGS. 18 and 20 , forexample, sample preforms were curved into 3D shapes. It was found thatthe systems and methods of this disclosure significantly lowered theforming temperature required compared to conventional preform-basedvacuum forming methods, and excellent quality, as measured by surfaceroughness, was also achieved. In particular, using the conventionalpreform-based vacuum forming method, a forming temperature of around800° C. was required when using a glass preform made of Gorilla Glass®with a thickness of 2.0 mm, and a surface roughness of less than 3.0 nmwas achieved for the concave surface of the curved preform. In contrast,using the systems and methods discussed herein, the forming temperaturewas around 700° C. for a glass preform made of the same material andthickness, and the surface roughness was less than 1.5 nm.

In some embodiments of this disclosure, to conform a mirror preform tothe forming surface, vacuum pressure is supplied through one or morevacuum holes, as discussed above. However, the vacuum holes can leavemanufacturing artifacts in the form of imperfections where the substratecontracted the vacuum holes. Thus, mold may not include vacuum holes inan area that will contact the effective area of the mirror preform or 3Dmirror. Instead, the mold can have one or more vacuum holes in an areaof the mold that does not contact the effective area, such as at theperimeter of the forming surface adjacent to an area near the edge ofthe 3D mirror. In some embodiments, a ditch-type vacuum hole can be usedat a periphery of the forming surface. As used herein, the effectivearea is a portion of the mirror or mirror substrate that will reflectthe image to be projected and primarily viewed by the user.

The reflective surface can be formed via sputtering, evaporation (e.g.,CVD, PVD), plating, or other methods of coating or supplying areflective surface known to those of ordinary skill in the art. Thereflective surface can include one or more metals, metallic/ceramicoxides, metallic/ceramic alloys, for example. The reflective coating caninclude aluminum or silver. The reflective surface is formed on the 3Dformed substrate after forming the substrate to a curved or asphericshape. However, embodiments are not limited to this order, and it iscontemplated that a 3D mirror can be formed from a 2D preform having areflective surface.

The glass-based substrate has a thickness that is less than or equal to3.0 mm; from about 0.5 mm to about 3.0 mm; from about 0.5 mm to about1.0 mm; or from about 1.0 mm to about 3.0 mm.

Suitable glass substrates for mirrors in HUD systems can benon-strengthened glass sheets or can also be strengthened glass sheets.The glass sheets (whether strengthened or non-strengthened) may includesoda-lime glass, aluminosilicate, boroaluminosilicate or alkalialuminosilicate glass. Optionally, the glass sheets may be thermallystrengthened. In embodiments where soda-lime glass is used as thenon-strengthened glass sheet, conventional decorating materials andmethods (e.g., glass frit enamels and screen printing) can be used

Suitable glass substrates may be chemically strengthened by an ionexchange process. In this process, typically by immersion of the glasssheet into a molten salt bath for a predetermined period of time, ionsat or near the surface of the glass sheet are exchanged for larger metalions from the salt bath. In one embodiment, the temperature of themolten salt bath is about 430° C. and the predetermined time period isabout eight hours. The incorporation of the larger ions into the glassstrengthens the sheet by creating a compressive stress in a near surfaceregion. A corresponding tensile stress is induced within a centralregion of the glass to balance the compressive stress.

Exemplary ion-exchangeable glasses that are suitable for forming glasssubstrates are soda lime glasses, alkali aluminosilicate glasses oralkali aluminoborosilicate glasses, though other glass compositions arecontemplated. As used herein, “ion exchangeable” means that a glass iscapable of exchanging cations located at or near the surface of theglass with cations of the same valence that are either larger or smallerin size. One exemplary glass composition comprises SiO2, B2O3 and Na2O,where (SiO2+B2O3)≥66 mol. %, and Na2O≥9 mol. %. In an embodiment, theglass sheets include at least 6 wt. % aluminum oxide. In a furtherembodiment, a glass sheet includes one or more alkaline earth oxides,such that a content of alkaline earth oxides is at least 5 wt. %.Suitable glass compositions, in some embodiments, further comprise atleast one of K2O, MgO, and CaO. In a particular embodiment, the glasscan comprise 61-75 mol. % SiO2; 7-15 mol. % Al2O3; 0-12 mol. % B2O3;9-21 mol. % Na2O; 0-4 mol. % K2O; 0-7 mol. % MgO; and 0-3 mol. % CaO.

A further exemplary glass composition suitable for forming glasssubstrates comprises: 60-70 mol. % SiO2; 6-14 mol. % Al2O3; 0-15 mol. %B2O3; 0-15 mol. % Li2O; 0-20 mol. % Na2O; 0-10 mol. % K2O; 0-8 mol. %MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO2; 0-1 mol. % SnO2; 0-1 mol. % CeO2;less than 50 ppm As2O3; and less than 50 ppm Sb2O3; where 12 mol.%≤(Li2O+Na2O+K2O)≤20 mol. % and 0 mol. %≤(MgO+CaO)≤10 mol. %.

A still further exemplary glass composition comprises: 63.5-66.5 mol. %SiO2; 8-12 mol. % Al2O3; 0-3 mol. % B2O3; 0-5 mol. % Li2O; 8-18 mol. %Na2O; 0-5 mol. % K2O; 1-7 mol. % MgO; 0-2.5 mol. % CaO; 0-3 mol. % ZrO2;0.05-0.25 mol. % SnO2; 0.05-0.5 mol. % CeO2; less than 50 ppm As2O3; andless than 50 ppm Sb2O3; where 14 mol. %≤(Li2O+Na2O+K2O)≤18 mol. % and 2mol. %≤(MgO+CaO)≤7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass comprisesalumina, at least one alkali metal and, in some embodiments, greaterthan 50 mol. % SiO2, in other embodiments at least 58 mol. % SiO2, andin still other embodiments at least 60 mol. % SiO2, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1},$wherein in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass, in particularembodiments, comprises, consists essentially of, or consists of: 58-72mol. % SiO2; 9-17 mol. % Al2O3; 2-12 mol. % B2O3; 8-16 mol. % Na2O; and0-4 mol. % K2O, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1}.$

In another embodiment, an alkali aluminosilicate glass comprises,consists essentially of, or consists of: 61-75 mol. % SiO2; 7-15 mol. %Al2O3; 0-12 mol. % B2O3; 9-21 mol. % Na2O; 0-4 mol. % K2O; 0-7 mol. %MgO; and 0-3 mol. % CaO.

In yet another embodiment, an alkali aluminosilicate glass substratecomprises, consists essentially of, or consists of: 60-70 mol. % SiO2;6-14 mol. % Al2O3; 0-15 mol. % B2O3; 0-15 mol. % Li2O; 0-20 mol. % Na2O;0-10 mol. % K2O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol. % ZrO2; 0-1mol. % SnO2; 0-1 mol. % CeO2; less than 50 ppm As2O3; and less than 50ppm Sb2O3; wherein 12 mol. %≤Li2O+Na2O+K2O≤20 mol. % and 0 mol.%≤MgO+CaO≤10 mol. %.

In still another embodiment, an alkali aluminosilicate glass comprises,consists essentially of, or consists of: 64-68 mol. % SiO2; 12-16 mol. %Na2O; 8-12 mol. % Al2O3; 0-3 mol. % B2O3; 2-5 mol. % K2O; 4-6 mol. %MgO; and 0-5 mol. % CaO, wherein: 66 mol. %≤SiO2+B2O3+CaO≤69 mol. %;Na2O+K2O+B2O3+MgO+CaO+SrO>10 mol. %; 5 mol. %≤MgO+CaO+SrO≤8 mol. %;(Na2O+B2O3)−Al2O3≤2 mol. %; 2 mol. %≤Na2O−Al2O3≤6 mol. %; and 4 mol.%≤(Na2O+K2O)—Al2O3≤10 mol. %.

The chemically-strengthened as well as the non-chemically-strengthenedglass, in some embodiments, can be batched with 0-2 mol. % of at leastone fining agent selected from a group that includes Na2SO4, NaCl, NaF,NaBr, K2SO4, KCl, KF, KBr, and SnO2.

In one exemplary embodiment, sodium ions in the chemically-strengthenedglass can be replaced by potassium ions from the molten bath, thoughother alkali metal ions having a larger atomic radii, such as rubidiumor cesium, can replace smaller alkali metal ions in the glass. Accordingto particular embodiments, smaller alkali metal ions in the glass can bereplaced by Ag+ ions. Similarly, other alkali metal salts such as, butnot limited to, sulfates, halides, and the like may be used in the ionexchange process.

The replacement of smaller ions by larger ions at a temperature belowthat at which the glass network can relax produces a distribution ofions across the surface of the glass that results in a stress profile.The larger volume of the incoming ion produces a compressive stress (CS)on the surface and tension (central tension, or CT) in the center of theglass. The compressive stress is related to the central tension by thefollowing relationship:

${CS} = {C{T\left( \frac{t - {2DOL}}{DOL} \right)}}$

where t is the total thickness of the glass sheet and DOL is the depthof exchange, also referred to as depth of layer.

According to various embodiments, glass substrates comprisingion-exchanged glass can possess an array of desired properties,including low weight, high impact resistance, and improved soundattenuation. In one embodiment, a chemically-strengthened glass sheetcan have a surface compressive stress of at least 300 MPa, e.g., atleast 400, 450, 500, 550, 600, 650, 700, 750 or 800 MPa, a depth oflayer at least about 20 μm (e.g., at least about 20, 25, 30, 35, 40, 45,or 50 μm) and/or a central tension greater than 40 MPa (e.g., greaterthan 40, 45, or 50 MPa) but less than 100 MPa (e.g., less than 100, 95,90, 85, 80, 75, 70, 65, 60, or 55 MPa).

A modulus of elasticity of a chemically-strengthened glass sheet canrange from about 60 GPa to 85 GPa (e.g., 60, 65, 70, 75, 80 or 85 GPa).If used in a glass-based laminate with a polymer interlayer, the modulusof elasticity of the glass sheet(s) and the polymer interlayer canaffect both the mechanical properties (e.g., deflection and strength)and the acoustic performance (e.g., transmission loss) of the resultingglass laminate structure.

Suitable glass substrates may be thermally strengthened by a thermaltempering process or an annealing process. The thickness of thethermally-strengthened glass sheets may be less than about 2 mm or lessthan about 1 mm.

Exemplary glass sheet forming methods include fusion draw and slot drawprocesses, which are each examples of a down-draw process, as well asfloat processes. These methods can be used to form both strengthened andnon-strengthened glass sheets. The fusion draw process uses a drawingtank that has a channel for accepting molten glass raw material. Thechannel has weirs that are open at the top along the length of thechannel on both sides of the channel. When the channel fills with moltenmaterial, the molten glass overflows the weirs. Due to gravity, themolten glass flows down the outside surfaces of the drawing tank. Theseoutside surfaces extend down and inwardly so that they join at an edgebelow the drawing tank. The two flowing glass surfaces join at this edgeto fuse and form a single flowing sheet. The fusion draw method offersthe advantage that, because the two glass films flowing over the channelfuse together, neither outside surface of the resulting glass sheetcomes in contact with any part of the apparatus. Thus, the surfaceproperties of the fusion drawn glass sheet are not affected by suchcontact.

The slot draw method is distinct from the fusion draw method. Here themolten raw material glass is provided to a drawing tank. The bottom ofthe drawing tank has an open slot with a nozzle that extends the lengthof the slot. The molten glass flows through the slot/nozzle and is drawndownward as a continuous sheet and into an annealing region. The slotdraw process can provide a thinner sheet than the fusion draw processbecause only a single sheet is drawn through the slot, rather than twosheets being fused together.

Down-draw processes produce glass sheets having a uniform thickness thatpossess surfaces that are relatively pristine. Because the strength ofthe glass surface is controlled by the amount and size of surface flaws,a pristine surface that has had minimal contact has a higher initialstrength. When this high strength glass is then chemically strengthened,the resultant strength can be higher than that of a surface that hasbeen a lapped and polished. Down-drawn glass may be drawn to a thicknessof less than about 2 mm. In addition, down drawn glass has a very flat,smooth surface that can be used in its final application without costlygrinding and polishing.

In the float glass method, a sheet of glass that may be characterized bysmooth surfaces and uniform thickness is made by floating molten glasson a bed of molten metal, typically tin. In an exemplary process, moltenglass that is fed onto the surface of the molten tin bed forms afloating ribbon. As the glass ribbon flows along the tin bath, thetemperature is gradually decreased until a solid glass sheet can belifted from the tin onto rollers. Once off the bath, the glass sheet canbe cooled further and annealed to reduce internal stress.

In some embodiments, exemplary glass substrates of embodiments discussedherein can be employed in vehicles (automobile, aircraft, and the like)having a Head-up or Heads-up Display (HUD) system. The clarity of fusionformed according to some embodiments can be superior to glass formed bya float process to thereby provide a better driving experience as wellas improve safety since information can be easier to read and less of adistraction. A non-limiting HUD system can include a projector unit, acombiner, and a video generation computer. The projection unit in anexemplary HUD can be, but is not limited to, an optical collimatorhaving a convex lens or concave mirror with a display (e.g., opticalwaveguide, scanning lasers, LED, CRT, video imagery, or the like) at itsfocus. The projection unit can be employed to produce a desired image.In some embodiments, the HUD system can also include a combiner or beamsplitter to redirect the projected image from the projection unit tovary or alter the field of view and the projected image. Some combinerscan include special coatings to reflect monochromatic light projectedthereon while allowing other wavelengths of light to pass through. Inadditional embodiments, the combiner can also be curved to refocus animage from the projection unit. Any exemplary HUD system can alsoinclude a processing system to provide an interface between theprojection unit and applicable vehicle systems from which data can bereceived, manipulated, monitored and/or displayed. Some processingsystems can also be utilized to generate the imagery and symbology to bedisplayed by the projection unit.

Using such an exemplary HUD system, a display of information (e.g.,numbers, images, directions, wording, or otherwise) can be created byprojecting an image from the HUD system onto an interior facing surfaceof a glass-based mirror substrate. The mirror can then redirect theimage so that it is in the field of view of a driver.

Exemplary glass substrates according to some embodiments can thusprovide a thin, pristine surface for the mirror. In some embodiments,fusion drawn Gorilla Glass can be used as the glass substrate. Suchglass does not contain any float lines typical of conventional glassmanufactured with the float process (e.g., soda lime glass).

HUDs according to embodiments of the present disclosure can be employedin automotive vehicles, aircraft, synthetic vision systems, and/or maskdisplays (e.g., head mounted displays such as goggles, masks, helmets,and the like) utilizing exemplary glass substrates described herein.Such HUD systems can project critical information (speed, fuel,temperature, turn signal, navigation, warning messages, etc.) in frontof the driver through the glass laminate structure.

According to some embodiments, the HUD systems described herein can usenominal HUD system parameters for radius of curvature, refractive index,and angle of incidence (e.g., radius of curvature Rc=8301 mm, distanceto source: Ri=1000 mm, refractive index n=1.52, and angle of incidenceθ=62.08o).

Aspect 1 of this disclosure pertains to a method of forming athree-dimensional mirror for a heads-up display (HUD) system, the methodcomprising: providing a glass-based preform having a first majorsurface, a second major surface opposite to the first major surface, anda minor surface connecting the first and second major surfaces, theminor surface comprising first and second longitudinal side surfacesopposite to each other and first and second transverse side surfacesconnecting the longitudinal side surfaces; disposing the glass-basedpreform on a mold having a concave surface such that the second majorsurface faces the concave surface of the mold, and such that the firstand second longitudinal side surfaces are adjacent to a longitudinalwall of a housing, the longitudinal wall extending from the concavesurface to at least a height of the second major surface of theglass-based preform; supplying a vacuum to a gap between the secondmajor surface and the concave surface; and conforming the second majorsurface to the concave surface of the mold using the vacuum, wherein thefirst and second transverse side surfaces have a curved shapecorresponding to a curve of the concave surface such that the first andsecond transverse side surfaces remain coincident with the concavesurface during the conforming of the second major surface.

Aspect 2 of this disclosure pertains to the method of Aspect 1, whereinthe concave surface comprises at least one opening for supplying avacuum to the gap.

Aspect 3 of this disclosure pertains to the method of Aspect 1 or Aspect2, wherein the longitudinal wall of the housing prevents leakage of thevacuum at a portion of the gap between the first longitudinal sidesurface and the concave surface, and between the second longitudinalside surface and the concave surface.

Aspect 4 of this disclosure pertains to the method of any one of Aspects1-3, wherein the concave surface of the mold comprises a first radius ofcurvature for a first curvature running in a longitudinal direction ofthe mold, and a second radius of curvature for a second curvaturerunning in a transverse direction of the mold, the second radius ofcurvature being larger than the first radius of curvature.

Aspect 5 of this disclosure pertains to the method of any one of Aspects1-4, wherein the concave surface is shaped such that, during conforming,a distance between the first and second longitudinal side surfaces ofthe glass-based preform decreases less than a distance between the firstand second transverse side surfaces of the glass-based preform.

Aspect 6 of this disclosure pertains to the method of any one of Aspects1-5, wherein a transverse wall of the housing prevents leakage of thevacuum at a portion of the gap between the first transverse side surfaceand the concave surface, and between the second transverse side surfaceand the concave surface.

Aspect 7 of this disclosure pertains to the method of any one of Aspects1-6, wherein clearance between the housing and the minor surface is lessthan about 0.5 mm.

Aspect 8 of this disclosure pertains to the method of any one of Aspects1-7, wherein the curved shape of at least one of the first and secondtransverse side surfaces comprises a single radius of curvature.

Aspect 9 of this disclosure pertains to the method of any one of Aspects1-8, wherein the curved shape of at least one of the first and secondtransverse side surfaces comprises a spline curve.

Aspect 10 of this disclosure pertains to the method of any one ofAspects 1-9, wherein the three-dimensional mirror is not cut afterconforming the second major surface such that the three-dimensionalmirror for the HUD system has a first major surface that is concavelyshaped, a second major surface opposite to the first major surface, anda minor surface connecting the first and second major surfaces, theminor surface corresponding to the minor surface of the glass preform.

Aspect 22 of this disclosure pertains to the method of any one ofAspects 1-10, wherein at least a portion of the first major surface is areflective surface.

Aspect 12 of this disclosure pertains to the method of Aspect 11,wherein the reflective surface comprises a metal, a metallic oxide, aceramic oxide, or a metallic-ceramic oxide disposed on the first majorsurface.

Aspect 13 of this disclosure pertains to the method of Aspect 12,wherein the metallic layer comprises Al, Ag, TiO2, or SiO2.

Aspect 14 of this disclosure pertains to the method of any one ofAspects 1-13, wherein the conforming of the second major surface to theconcave surface of the mold is performed at a temperature below theglass transition temperature of the glass-based substrate.

Aspect 15 of this disclosure pertains to the method of Aspect 14,wherein the temperature is about 5° C. to 30° C. below the glasstransition temperature of the glass-based substrate.

Aspect 16 of this disclosure pertains to the method of Aspect 15,wherein the temperature is about 10° C. to 20° C. below the glasstransition temperature of the glass-based substrate.

Aspect 17 of this disclosure pertains to the method of any one ofAspects 1-16, further comprising forming a reflective surface on thefirst major surface after the conforming of the second major surface tothe concave surface.

Aspect 18 of this disclosure pertains to an apparatus for forming athree-dimensional mirror for a heads-up display (HUD), comprising: amold comprising a concave surface with at least one opening configuredto supply a vacuum to a space above the concave surface when aglass-based preform is disposed on the mold; and a housing adjacent toand at least partially surrounding the concave surface, the housingextending from the concave surface to at least a height of theglass-based preform when the mirror preform is disposed on the mold,

wherein the housing is sized to prevent leakage of the vacuum at aportion of the space between the glass-based preform and the concavesurface.

Aspect 19 of this disclosure pertains to the apparatus of Aspect 18,wherein the housing comprises first and second longitudinal side wallsalong opposite longitudinal sides of the concave surface.

Aspect 20 of this disclosure pertains to the apparatus of Aspect 18 orAspect 19, wherein the housing comprises first and second transverseside walls along opposite transverse sides of the concave surface, thefirst and second transverse side walls being curved to a shapecorresponding to a curve of first and second edges of the glass-basedpreform.

Aspect 21 of this disclosure pertains to the apparatus of any one ofAspects 18-20, wherein the support surface has an aspheric shapeconfigured to conform the glass-based preform to an aspheric shape.

Aspect 22 of this disclosure pertains to a method of forming an asphericmirror from a two-dimensional glass-based preform, the methodcomprising: providing a glass-based preform comprising a first majorsurface, a second major surface opposite the first major surface, and aminor surface connecting the first and second major surfaces, the minorsurface comprising first and second longitudinal side surfaces oppositeto each other and first and second transverse side surfaces connectingthe longitudinal side surfaces the glass-based preform having asubstantially two-dimensional shape; disposing the glass-based preformon a lower mold comprising a curved surface having an aspheric shapefacing the second major surface, the lower mold being configured tosupply a vacuum to a gap between the curved surface and the second majorsurface; and performing a primary forming step by supplying vacuumpressure to the gap while a shell surrounds the glass-based preform suchthat a substantially vertical wall of the shell extends from the curvedsurface to at least the second major surface, the substantially verticalwall facing the minor surface; wherein the substantially vertical wallof the shell is spaced from the minor surface at a distance to improvethe vacuum pressure in the gap.

Aspect 23 of this disclosure pertains to the method of Aspect 22,further comprising: performing a secondary forming step by applying aclamping-ring to a periphery portion of the first major surface to holdthe second major surface against the curved surface at the peripheryportion, wherein the second forming step is performed while the lowermold is supplying a vacuum to the gap.

Aspect 24 of this disclosure pertains to the method of Aspect 23,wherein the second forming step is performed after the first formingstep.

Aspect 25 of this disclosure pertains to the method of any one ofAspects 22-24, wherein the first and second traverse side surfaces havea curved shape corresponding to a curvature of the curved surface of thelower mold, and wherein the curved shape of the first and secondtransverse side surfaces remains substantially coincident with thecurved surface during the primary forming step.

Aspect 26 of this disclosure pertains to the method of any one ofAspects 22-25, further comprising placing the shell on a lower supportmember configured to lower the shell onto the lower mold for the primaryforming step.

Aspect 27 of this disclosure pertains to the method of any one ofAspects 23-26, further comprising placing the clamping-ring on theglass-based preform using a lower support member configured to lower theclamping-ring onto the glass-based preform for the secondary formingstep.

Aspect 28 of this disclosure pertains to the method of any one ofAspects 22-27, further comprising heating the glass-based preform duringthe primary forming step.

Aspect 29 of this disclosure pertains to the method of any one ofAspects 23-28, further comprising heating the glass-based preform duringthe primary and secondary forming steps.

Aspect 30 of this disclosure pertains to the method of Aspect 29,wherein a temperature of heating the glass-based preform during thesecondary forming step is lower than a temperature of heating theglass-based preform during the primary forming step.

Aspect 31 of this disclosure pertains to the method of Aspect 28,wherein a heater is disposed above the lower mold facing the first majorsurface of the glass-based preform.

Aspect 32 of this disclosure pertains to the method of Aspect 30,wherein a heater is disposed above the lower mold facing the first majorsurface of the glass-based preform.

Aspect 33 of this disclosure pertains to the method of any one ofAspects 22-32, wherein the aspheric mirror is not cut after the primaryforming step.

Aspect 34 of this disclosure pertains to the method of any one ofAspects 22-33, wherein the first major surface comprises a reflectivesurface.

Aspect 35 of this disclosure pertains to the method of Aspect 34,wherein the reflective surface comprises a metal, a metallic oxide, aceramic oxide, or a metallic-ceramic oxide.

Aspect 36 of this disclosure pertains to the method of Aspect 35,wherein the metal is Al, Ag, TiO2, or SiO2.

Aspect 37 of this disclosure pertains to the method of any one ofAspects 22-36, wherein the distance that the substantially vertical wallof the shell is spaced from the minor surface is less than or equal to 1mm.

Aspect 38 of this disclosure pertains to the method of any one ofAspects 22-37, wherein the distance that the substantially vertical wallof the shell is spaced from the minor surface is less than 1 mm.

Aspect 39 of this disclosure pertains to the method of any one ofAspects 30-38, wherein the temperature of heating the glass-basedpreform during the secondary forming step is less than the glasstransition temperature of the glass-based preform.

Aspect 40 of this disclosure pertains to the method of Aspect 39,wherein the temperature of heating the glass-based preform during thesecondary forming step is about 5° C.-20° C. below the glass transitiontemperature of the glass-based preform.

Aspect 41 of this disclosure pertains to the method of any one ofAspects 22-40, wherein the vacuum pressure is from 70 to 90 kPa.

Aspect 42 of this disclosure pertains to the method of any one ofAspects 23-41, wherein the clamping-ring comprises first and secondcurved surfaces corresponding to first and second portions of the curvedsurface of the lower mold, the first and second curved surface beingshaped to hold the periphery portion in contact with the lower mold toimprove the vacuum pressure.

Aspect 43 of this disclosure pertains to the method of any one ofAspects 22-42, wherein a length of the first and second longitudinalside surfaces is greater than a length of the first and secondtransverse side surfaces.

Aspect 44 of this disclosure pertains to the method of any one ofAspects 22-43, wherein the aspheric mirror is a mirror for a heads-updisplay (HUD).

Aspect 45 of this disclosure pertains to a glass-based three-dimensional(3D) mirror for a heads-up display (HUD) system formed according to anyone of Aspects 1-17 and 22-44.

Aspect 46 of this disclosure pertains to the mirror of Aspect 45,wherein the glass-based preform has a thickness that is less than orequal to 3.0 mm.

Aspect 47 of this disclosure pertains to the mirror of Aspect 46,wherein the thickness of the glass-based preform is from about 0.5 mm toabout 3.0 mm.

Aspect 48 of this disclosure pertains to the mirror of Aspect 47,wherein the thickness of the glass-based preform is from about 0.5 mm toabout 1.0 mm.

Aspect 49 of this disclosure pertains to the mirror of Aspect 47,wherein the thickness of the glass-based preform is from about 1.0 mm toabout 3.0 mm.

Aspect 50 of this disclosure pertains to the mirror of any one ofAspects 45-49, wherein the mirror has a first radius of curvature suchthat the first major surface has a concave shape and the second majorsurface has a convex shape, the first radius of curvature being relativeto a first axis of curvature.

Aspect 51 of this disclosure pertains to the mirror of Aspect 50,wherein the mirror has a second radius of curvature that is relative toa second axis of curvature different from the first axis of curvature.

Aspect 52 of this disclosure pertains to the mirror of Aspect 51,wherein the first axis of curvature is perpendicular to the second axisof curvature.

Aspect 53 of this disclosure pertains to the mirror of any one ofAspects 45-51, wherein the first major surface has an aspheric shape.

Aspect 54 of this disclosure pertains to the mirror of any one ofAspects 45-53, wherein the glass-based preform comprises strengthenedglass.

Aspect 55 of this disclosure pertains to the glass-based preform ofAspect 54, wherein the strengthened glass is chemically strengthened.

While this description may include many specifics, these should not beconstrued as limitations on the scope thereof, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that have been heretofore described in the context ofseparate embodiments may also be implemented in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiment may also be implemented in multipleembodiments separately or in any suitable sub-combination. Moreover,although features may be described above as acting in certaincombinations and may even be initially claimed as such, one or morefeatures from a claimed combination may in some cases be excised fromthe combination, and the claimed combination may be directed to asub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings or figures in aparticular order, this should not be understood as requiring that suchoperations be performed in the particular order shown or in sequentialorder, or that all illustrated operations be performed, to achievedesirable results. In certain circumstances, multitasking and parallelprocessing may be advantageous

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, examples include from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

It is also noted that recitations herein refer to a component of thepresent disclosure being “configured” or “adapted to” function in aparticular way. In this respect, such a component is “configured” or“adapted to” embody a particular property, or function in a particularmanner, where such recitations are structural recitations as opposed torecitations of intended use. More specifically, the references herein tothe manner in which a component is “configured” or “adapted to” denotesan existing physical condition of the component and, as such, is to betaken as a definite recitation of the structural characteristics of thecomponent.

As shown by the various configurations and embodiments illustrated inthe figures, various glass-based structures for head-up displays havebeen described.

While preferred embodiments of the present disclosure have beendescribed, it is to be understood that the embodiments described areillustrative only and that the scope of the invention is to be definedsolely by the appended claims when accorded a full range of equivalence,many variations and modifications naturally occurring to those of skillin the art from a perusal hereof.

The invention claimed is:
 1. A method of forming a three-dimensionalmirror for a heads-up display (HUD) system, the method comprising:providing a glass-based preform having a first major surface, a secondmajor surface opposite to the first major surface, and a minor surfaceconnecting the first and second major surfaces, the minor surfacecomprising first and second longitudinal side surfaces opposite to eachother and first and second transverse side surfaces connecting thelongitudinal side surfaces; disposing the glass-based preform on a moldhaving a concave surface such that the second major surface faces theconcave surface of the mold, and such that the first and secondlongitudinal side surfaces are adjacent to a longitudinal wall of ahousing, the longitudinal wall extending from the concave surface to atleast a height of the second major surface of the glass-based preform,wherein the concave surface comprises at least one opening for supplyinga vacuum to a gap between the second major surface and the concavesurface; supplying a vacuum to the gap; and conforming the second majorsurface to the concave surface of the mold using the vacuum, wherein theat least one opening for supplying the vacuum to the gap does notcontact an effective area of the three-dimensional mirror, wherein thefirst and second transverse side surfaces have a curved shapecorresponding to a curve of the concave surface such that the first andsecond transverse side surfaces contact the concave surface when theglass-based preform is disposed on the mold in a two-dimensional shapeand remain coincident with the concave surface during the conforming ofthe second major surface, wherein the glass-based preform is not cutafter the conforming.
 2. A method of forming an aspheric mirror from atwo-dimensional glass-based preform, the method comprising: providing aglass-based preform comprising a first major surface, a second majorsurface opposite the first major surface, and a minor surface connectingthe first and second major surfaces, the minor surface comprising firstand second longitudinal side surfaces opposite to each other and firstand second transverse side surfaces connecting the longitudinal sidesurfaces; disposing the glass-based preform on a lower mold comprising acurved surface having an aspheric shape facing the second major surfacewhen the glass-based preform has a two-dimensional shape, the lower moldbeing configured to supply a vacuum to a gap between the curved surfaceand the second major surface via one or more openings on the curvedsurface; and performing a primary forming step by supplying a vacuumpressure to the gap while a shell surrounds the glass-based preform suchthat a wall of the shell extends from the curved surface to at least thesecond major surface when the glass-based preform has thetwo-dimensional shape, the wall facing the minor surface; wherein theone or more openings for supplying the vacuum to the gap does notcontact an effective area of the aspheric mirror, and wherein the wallof the shell is spaced from the minor surface by a distance that is lessthan 0.5 mm.
 3. The method of claim 2, further comprising: performing asecondary forming step by applying a clamping-ring to a peripheryportion of the first major surface to hold the second major surfaceagainst the curved surface at the periphery portion, wherein thesecondary forming step is performed while the lower mold is supplyingthe vacuum pressure to the gap.
 4. The method of claim 3, wherein thesecond forming step is performed after the primary forming step.
 5. Themethod of claim 2, wherein the first and second traverse side surfaceshave a curved shape corresponding to a curvature of the curved surfaceof the lower mold, and wherein the curved shape of the first and secondtransverse side surfaces remains coincident with the curved surfaceduring the primary forming step.
 6. The method of claim 2, furthercomprising placing the shell on a lower support member configured tolower the shell onto the lower mold for the primary forming step.
 7. Themethod of claim 3, further comprising placing the clamping-ring on theglass-based preform using a lower support member configured to lower theclamping-ring onto the glass-based preform for the secondary formingstep.
 8. The method of claim 3, further comprising heating theglass-based preform during the primary and secondary forming steps. 9.The method of claim 2, wherein the aspheric mirror is not cut after theprimary forming step.
 10. The method of claim 2, further comprisingforming a reflective surface on the first major surface.
 11. The methodof claim 10, wherein the reflective surface comprises a metal, ametallic oxide, a ceramic oxide, or a metallic-ceramic oxide.
 12. Themethod of claim 2, wherein the distance that the wall of the shell isspaced from the minor surface is less than or equal to 1 mm.
 13. Themethod of claim 2, wherein the vacuum pressure is from 70 to 90 kPa. 14.The method of claim 3, wherein the clamping-ring comprises first andsecond curved surfaces corresponding to first and second portions of thecurved surface of the lower mold, the first and second curved surfacebeing shaped to hold the periphery portion in contact with the lowermold to improve the vacuum pressure.
 15. The method of claim 2, whereina length of the first and second longitudinal side surfaces is greaterthan a length of the first and second transverse side surfaces.
 16. Aglass-based three-dimensional (3D) mirror for a heads-up display (HUD)system formed according to claim 2.